URGENT ! add selected fields in a table.

Hi,

I have a long table itab like this :

________________________________________

Plant Storage Material Batch Credit Debit ________________________________________

103 1001 125 PDX 00 15

103 1001 125 PEX 00 15

103 1001 125 PEX 00 15

103 1001 125 PEX 25 00

103 1001 226 PDX 00 15

...

When Plant, Storage, Material and Batch are equal I have to make sum of credit and debit and give balance (credit - debit) like this :

Plant Storage Material Batch Credit Debit Bal ____________________________________________

103 1001 125 PDX 00 15 -15

103 1001 125 PEX 25 30 -5

103 1001 226 PDX 00 15 -15

...

It's urgent, can you tell me how to code this? Points awarded!

Tarick.